Paint spray gun



De 31, 1963 s. R. ROSEN E'rAl. 3,116,020

PAINT SPRAY GUN Filed Oct. 5, 1961 v 2-Sheets-Sheet 1 /f 7J W 4? f 3 l im l l 65 62 N Y --ff i Q 64 58 C A72- W Arme/vir l Dec. 3l, 1963 s. R. RosEN ETAI. 3,116,020

PAINT SPRAY GUN Filed Oct. 5, 1961 2 Sheets-Sheet 2 /Ma f M' United States Patent O 3,1%,926 PAINT SPRAY GUN Samuel R. Rosen, Lorain, and Eric T. Nord, Oberlin, (Ehio, assignors to Nordson Corporation, Amherst, hio, a corporation of Qhio Filed Oct. 5, 1961, Ser. No. 154,382 It) Claims. (Cl. 239-578) This yinvention relates to spray guns and particularly comprehends the class thereof wherein liquid, such as hot paint is introduced to and contained in the chamber of the gun at high pressure and is intended to be shot from the gun at frequent intervals by manual or remotely controlled trigger actuation. Our invention comprises an improvement upon some aspects of our prior spray gun invention patented in our prior Patent No. 2,936,959 issued May 17, 1960.

A problem which has plagued this art, among others, has been the actuation and/or movement of means disposed within a high pressure vessel or chamber by means disposed outside the same. In the art of spraying paint by projecting liquid paint from a high pressure chamber in a `spray gun, this problem takes the specific form of actuating a discharge valve which has its closure element within `the chamber, by the manual motion of a trigger or lever disposed and movable externally of the chamber. The problem is aggravated when the paint is hot because of expansion and contraction, the increased tendency of the hot paint to leak through glands, gaskets and seals, the fact that paint solvents degrade elastomeric (rubberl-ike) substances and the manual diiicul-ty of handling a hot gun. The problem is also aggravated by the fact that various so-called paints have abrasive constituents which tend to destroy seals, packing, valves and orifices as well as all other mechanisms exposed to lthe paint where relative sliding contacts, ts and motions are involved.

Another problem confronting this art, and to a solution of which our prior patent was particularly addressed, was that of obtaining desirable spray patterns on the one hand, and the absence of spitting and/or dripping paint on the other hand. These problems appear to begin with, or be aggravated by, insufficient speed of movement of the discharge valve closure member relative to the seat incident to starting and stopping the discharge of liquid from the gun. In our present invention, we have provided a different and more simple solution to this problem than We taught and patented in our prior patent. Among the other problems which our invention has solved has been those of and incident to the weight and complicated structure of spray guns for our purpose, the awkwardness imposed by the connection of 4the gun 4with relatively stiff, high-pressure hoses and the inexibility of connections for such hoses for the varied uses and purposes to which high pressure guns are sought to be applied.

The objects of our invention include the solutions of the problems mentioned above as well as the provision of mechanisms and means for so doing which are economical 4to manufacture, use and maintain and which may be embodied in a gun of advantageous convenience, lightness, balance and facility.

A more specific object of our invention is to provide means for transmitting force and motion from without to Within the high pressure chamber of a hot paint spray gun with high mechanical and hydraulic efficiency without significant or deleterious waste of energy and without significant or deleterious loss of paint. A more specic object is to have the valve closing spring and closure member in the high pressure chamber and to actuate the same without substantial frictional losses, tas by a slender, small-diameter, tension element penetrating the wall of the chamber which will be Vsubstantially uninfluenced by lihZ@ Patented Dec. 31, 1963 ICC iiuid pressure within or without .the chamber. Another object is to employ the high iiuid pressure in the chamber to iniiuence the opening and closing of the Valve advantageously. A collateral object of our invention is to effect a fluid sea-l between the moving valve actuating element and the chamber wall through which it passes, having little friction, no leakage and long life as well as no deleterious e'fect on the parts between which the seal works.

Another object is to provide quite rapid opening and closing action of the discharge valve which controls the outflow of Huid from the high pressure chamber of our gun. Similarly, it is one of our objects to gain and insure spit-free operation and promote atomization tending to give tailafree and well-feathered delivery and discharge of paint from our gun in respect to the surface being painted or coated.

Another object is to gain some or all of the foregoing objects and also have a substantially elfort-less, or nontiring, trigger effort to trigger the gun on the one hand and to hold the discharge valve open on the other hand. A companion object is to obtain a snap-action opening and closing motion of the valve closure member characterized by a beneciently high acceleration toward and away from, and -into and out of engagement with, the valve seat whereby to approach instantaneous starting and stopping of the flow of paint or other fluid from the high pressure chamber of our gun.

Another object is to provide an 4improved connection, and facility and choice of connections, between paint conducting hoses and our gun. Within this object we aim to enhance the angular relation and choice of relations between the hoses and the barrel and grip of the gun both axially and circumferentially, and rotationally. More specifically, we desire to provide choice between having the hoses connect to the gun from above or below, from before or behind, to swivel at -their points of connection with the gun and to have an inclination `and disposition to accommodate the natural most desirable feel of the operator for his least vfatiguing eiort by the use of the gun.

These Iand other objects and advantages of our invention will more fully and at large appear from the following description of a preferred form and embodiment of our invention, reference being had to the accompanying drawings, in which:

FIGURE 1 is a side elevation, partly in longitudinal section, of a spray gun embodying our invention with downwardly and rearwardly extending connectors for paint hoses.

FIGURE 2 is a front elevation of the gun disclosed in FIGURE l.

FIGURE 2a corresponds to FIGURE 2 with the barrel removed.

FlGURE 3 is an expanded view of (a) the Valve assembly detached from, aligned with and moved leftwardly in the iigure from (b) the pre-assembled sealing oartridge of the valve actuating and sealing mechanism therefor shown in the right part of the lfigure.

FIGURE 4 is an enlarged longitudinal sectional view of the pre-assembled cartridge of the Valve actuating and sealing mechanism shown in the right portion of FIGURE 3.

FIGURE 5 is a rear elevation of the barrel of the gun removed from its attachment with the gun tas shown in FIGS. 1 and 2.

FIGURE 6 is a perspective view on a reduced scale of the gun embodying our invention with the hose connections and hoses depending downwardly and rearwardly from the pressure chamber of the barrel of the gain as shown in FIGS. 1 and 2.

FIGURE 7 is a View similar to FIG. 6 of the same gun with, however, the barrel turned over so that the hose connectors and hoses extend upwardly from the gun; and

FIGURE 8 is a view similar to FIGS. 6 and 7 with, however, the hose connectors and hoses extending rearwardly over the top of the gun.

In this description of a preferred form of our invention it will be convenient to use the word, paint, as illustrative and characteristic of all liquids and uids for which our gun is useful, including the same at hot as well as relatively cold temperatures and in various mixtures and solutions, such as pigmented lacquers, resins, vinyls and enamels with their various thinners, reducers, driers, and solvents. We shall also employ the term, paint, to include familiar oil based paints as well as the paints and coating materials described and illustrated in method patent, U.S. No. 2,754,228, lin the use of which method our gun has particular, though by no means exclusive, utility.

Our gun G, FIGS. 1, 2 and 6 8, comprises a hand grip R with an integrally formed stock S, having, conveniently, a suspension hook K at the top of the stock, a trigger T pivotally swinging about and depending from a pivot pin It) near the top of the stock, a barrel B removably and selectively attached to the forward end of the stock, a spray nozzle N at the extreme forward end of the barrel with the discharge valve V adjacent thereto within the barrel and controlling the ow of paint through the nozzle; the barrel also embracing the central chamber, i. e. the high pressure 'fluid chamber C, to which paint is conducted, and/or through which paint is circulated, by hoses H, FIGS. 6-8, via connectors 11 and 12, also FIGS. 1, 2 and 5, that have swivel mechanical connection with the barrel B and free fluid connection with the chamber C. Angled connectors 13 and 14, FIG. 8, otherwise similar to the connectors 11 and i2 lead the hose H rearwardly over the top of the gun. Our gun also has valve actuating mechanism interposed between the trigger T and valve V comprising the high-tensilestrength wire W, FIGS. l, 3 and 4, which passes from within to without the chamber and barrel at the rearward ends thereof through the packing assembly or cartridge P and with a free sliding, leak-proof t therein. The actuating wire W is connected at its forward end to the valve closure member 1S through the collar and chuck member 16, and is connected at its rearward end to the anchor and chuck member 17 that is engaged by the trigger T. Spring 2i) stressed in compression holds the closure l tightly on the seat 21 of the valve V, stresses the actuating wire W in tension and holds the trigger T in its foremost cocked position when the gun is ready to be fired or triggered but while the discharge valve is closed. Squeezing the trigger and swinging it rearwardly pulls the closure l5 oif the seat 21 to effect discharge of paint from the chamber C through the valve V to spray into atmosphere through the nozzle N according to the pattern and form imposed, inter alia, by the nozzle.

Referring now to FIGS. 1, 3 and 4, the barrel B carries the packing cartridge P in a rearwardly disposed bore 22; the cylindrical body part 23 of the cartridge having an external groove with an O-ring 24 which effects a fluid tight seal between the outside of the cartridge and the bore 22. The forwar end of the body 23 of the cartridge comprises an enlarged terminal flange 25 which bears axially against the shoulder 26 in the barrel at the forward end of the bore 22 and at the rearward end of the counterbore 27 which describes the main cylindrical part of the chamber C within the barrel. Fluid pressure in the chamber C as well as the stress and compression of the spring 2t? urges the body 23 of the cartridge and the rearward face of the flange 25 against the shoulder 26 tending to hold the same in xed relation to the barrel at all times during the operation of the gun.

Forwardly of the smooth cylindrical counterbore 27 the barrel has internal threads 28, preferably of greater diameter than the counterbore 27 wherein to threadably receive the enlarged rearward end 29 of the valve assembly V and make a fluid tight assembly with the barrel' between the mutually tapered seats 39 thereof. As shown'- in FIG. l the external threads on the enlarged rear end of the valve assembly V occupy not more than abouti half of the internal threads 28 when the valve assembly' is seated fluid tight in relation to the barrel on the seats 30. This leaves the foremost half portion of the threads 23 available to receive the external threads of the enlarged rearward end of the restrictor assembly 33 with the rearmost end of the restrictor assembly spaced from bottoming Contact with the enlarged end 29 of the valve assembly so that the restrictor disc 34 carried in the forward end of the restrictor assembly 33 may have tight bottoming contact with the forward end of the valve assembly V when the parts are assembled together as shown or suggested in FIG. 1. The forward end of the restrictor assembly 33 is assembled to receive the hollow nut 35 which detachably secures the nozzle N to the extreme forward end of the gun in tight, axially aligned Contact with the restrictor assembly 33, restrictor disc 34 and valve seat 21. We will revert again to the nozzle and restrictor assembly and the coaction between the same and the valve V. Presently our description shall proceed with the coaction between the barrel, valve, packing cartridge and trigger wherewith the gun is cocked, fired or held on or off The valve assembly V, FIGS. 1 and 4, comprises ther' enlarged rearward end 29 mentioned above and the for-l ward cylindrical portion 36 within the foremost end of which the hardened seat 2li and orice portion 38 is xedly and permanently secured. The part 37 embraces the seat 2li and the discharge orice 3S as well as a short, hollow, cylindrical portion within which the rounded, substantially spherical head 49 of the closure member 15 has wide and free clearance through which the paint may ow smoothly past and around the head and through the discharge orifice when the head is withdrawn from seating and closing contact with the seat 2li. The hollow forward portion of the valve assembly V has an enlarged and elongated open cylindrical interior in which the valve closure member l5' has a free, guided, sliding lit through a three legged, triple fluted guide 41. Rearwardly the valve assembly has an enlarged cylindrical interior p0rtion within the elongated rearward end 23 which accommodates the rearward threaded end 42 of the closure member 1.5 along with the collar and chuck member 1.6 with which it is threadably engaged and secured for operative connection with the actuating wire W and the packing cartride assembly, cf. FIGS. 1 and 3.

The chuck member 16 comprises in its forward portion the internally threaded bore 43 engaging the closure 15 and the external llange 44 against which the forward end of the spring 2@ has forcible bearing tending to close the valve. The rearward part of the member i6 comprises a split, externally tapered chuck or collet 45 having a small internal bore axially aligned with the axis of the valve V and cartridge P for releasably engaging the wire W when constrained to grip the same by coaction with the internally tapered ring 451' when the latter is driven into gripping rengagement with collet 45; the angles of the tapered, conical mating surfaces being below the critical for high mechanical advantage and desirably lasting engagement of the wire.

The body 23 of the cartridge has a central, solid wall portion le pierced forwardly by a small bore having a close, free sliding fit with the wire W, and pierced centrally and rearwardly by a small but larger diameter bore 47 having a tapered forward terminus wherein is contained the packing seal 48 and the spring-pressed, slidable gland i9 which has a tapered forward end, complementary to the taper of the forward end of the bore 47, bearing upon and compressing the rearward end of the seal 4S. The gland 49 has a neat close sliding tit in the bore 47 and has an internal bore which has a close, free, sliding iit with the wire W whereby the packing d is constrained between the wall 46, bore 47 and gland 49 under the forcible influence of the gland compressing spring 50 to have a tight, leak-proof sliding iit with the wire W. The bores of the wall, gland and packing have close axial alignment with the common axis of the cartridge and the valve. Forwardly of the wall 46 the body 23 affords a forwardly opening cylindrical chamber 52 in the rearward or bottom end of which the spring 20 is seated and into which and within the coils of the spring the chuck member 16 is freely movable. The rearward part of the body 2? comprises the chamber 53 for free reception of the enlarged head of the gland 49 and the coacting spring 50 and has internal threads for engagement with the external threads of an adjusting nut 54 by which the compression of the spring 50 may be desirably modified for the ecient compression of the packing seal 48. The nut 5d has a small bore axially aligned with the axis of the cartridge and affording a free sliding t with the wire W which passes therethrough.

The last portion of the packing cartridge assembly, FIGS. 1, 3 and 4, comprises a rearwardly disposed anchor 17 having an elongated cylindrical body portion 5' with a large internal bore that has a rearwardly opening tapered portion 56 receptive of the split collet-bushing 5'7 for releasably gripping and securing the wire W positively therein. The central bore of the bushing 57 is generally aligned with the axis of the cartridge as a whole, but the enlarged forward portion of the bore 56 permits freedom of movement of the Wire W therein admitting moderate angular displacement between the anchor 17 and the body 23 of the cartridge without risking deleterious kinking of the wire W in respect to its anchorage. As shown in FIG. 1, the trigger T is interposed between the nut 54 of the body 23 of the cartridge and the anchorportion 17 of the cartridge assembly; the trigger T having an anchor engaging element S8 carried on the rear side of the transverse face of the trigger and presenting an angled rounded edge straddling the wire W and having a small or approximately line contact with the forward face of the body 55 of the anchor 17 in approximately that plane of the wire W which is parallel with the axis of the pivot 10 of the trigger T. As also shown in FIG. l the body of the anchor 17 has a free sliding lit within a sleeve 60 which in turn is slidably carried in a fore and aft bore 61 in the stock S, all axially aligned with the common axis of the valve and cartridge. The rearward end of the bore 61 threadably receives an adjusting bolt 62 which with a lock nut 63 can position the sleeve 60 longitudinally of the bore and dispose the forward end of the sleeve to engage the element 5S to stay or permit the swinging of the trigger and/ or the movement of the anchor 17 and Wire W as may be desired. That is, were the sleeve 60 moved more leftwardly than viewed in FIG. l to be flush with the forward end of the anchor, the trigger would be held substantially immovable (with the valve V closed) between the sleeve 60 and the nut 54. Rightward positioning of the sleeve as viewed in FIG. 1 admits greater swinging of the trigger and, correspondingly, greater movement of the head 40 of the closure member from the seat 21 of the Valve V.

We gain additional and unexpected advantages in our invention by having regard, as we prefer, for the relative size and proportioning of certain of the parts above described, thus: In an exemplary gun embodying our invention the fluid pressure in the chamber C may be taken at about 1000 pounds per square inch, more or less, the wire W have a high tensile strength, about 100,000 pounds per square inch for example, and be made of stainless steel of about 0.026" in diameter, and the valve seat 21 be about 0.112 in diameter so that the effective area upon which pressure in the chamber exerts axial force on the closure member 15 is about 18 to 20 times as great as that of the wire W. Specically, 1000 pounds per square inch pressure in the chamber gives about l0 pounds closing pressure of the closure against the valve seat and about 1/2 pound pressure on the wire W tending to blow the wire out of the chamber. Moreover, the wire is so small (relatively) that great unitary radial sealing pressure exerted by the packing seal 4S upon the wire will develop little frictional drag thereupon, given, of course, desirably low-friction material in the packing and smooth surfaced wire W, such as ordinary single strand piano wire or commercial smooth drawn high tensile and/or stainless steel wire.

We prefer to employ the plastic resin, polytethaiiuoroethylene, sold under Du Ponts trademark, Teflon, for our packing seal 48 and to make the seal of small volume and in one solid piece, as about 1/s OD. and 5%16 maximum length with a central bore to tightly fit the wire and be shaped about as shown in FIG. 4 and entirely coniined in the bore 48 by the gland 49 except for quite close clearances, preferably about 0.002" between the bores of the wall 46 and gland 49, and the O D. of the wire W. With the spring 50 exerting about 20 pounds on the gland 49 to compress the packing seal 4S, and regarding the seal as a lluid of high viscosity, given time, the unit pressure created in the packing would tend to be about 1600 pounds per square inch. Because of the smallness of the wire W and the low coetiicient of friction between the smooth wire and the Teon of the seal there will be but a small or negligible frictional drag on the wire at the seal, and because the area of clearance between the wire and the bores of the wall and the gland adjacent the seal are so small and so long and thin, circumferentially and axially of the wire, the extrusion into and through the clearance is very slow, taking perhaps a year before impairing the eiiiciency of the seal. Meanwhile, the seal prevents any noticeable leakage of paint under pressure from the chamber along the wire at any of the temperatures or pressures desirably employed in the use of our gun. As suggested above, We contemplate pressures of the order of 1000 pounds per square inch, more or less, and temperatures from zero to about 450 F. according to the nature of the paint and the circumstances of the spraying.

Continuing this example, we may illustrate the snapaction which our gun affords at the critical instants of time of moving, i.e. accelerating, the head 40 of the closure member 15 from and to sealing contact with the seat 21 of the valve V. In our gun as mentioned above, the area of the valve seat is many times the area of the wire W and, for example, if the seat 21 be about .112 in diameter and about 0.010 square inch of elfective area, the pressure tending to hold the closure member on the seat when the valve is closed will be about 10 pounds (less about 1/2 pound exerted oppositely on the wire) when the fluid pressure in the chamber is 1000 pounds. To this is added the compression of the spring 20 which may conveniently be about 14 pounds, totaling about 231/2 pounds exerted by the closure 15 on the valve seat when the valve is closed. To open the valve, the operator will then have to squeeze the trigger T with a high initial squeeze suicient to overcome both the spring pressure and the fluid pressure which holds the valve closed. With a 3 to 1 leverage in the trigger and some friction to overcome, we reckon about 8 to 10 pounds iinger pressure will begin to open the valve. When, however, this force has begun to open the valve, then the force on the closure 15 which was tending to close the valve quickly drops from 10 pounds to zero as the head of the closure member moves away from the seat. Since, however, the lingers of the operator has to be stressed to overcome the 8 to 10 pound force, the fingers automatically continue to exert about the same squeeze whilst the resistance thereto quickly diminishes whereby the closure member is accelerated very rapidly away from the seat with an increasing force available to eiect that acceleration.

After the closure member has been moved from the seat to its desired open position, about 1/16 of an inch off the seat for illustrative purposes, the Work required of the fingers of the operator to maintain the valve thus opened is only that required to maintain the spring 2.0 compressed, i.e. about 1/s of 14 pounds spring pressure plus a little spring build-up, less the half pound blow-out pressure on the wire, which comes out at about 4 to 5 pounds. Thus we have provided a gun in which the operator by exerting only about 4 to 5 pounds pull on the trigger may hold the gun in the on position for long periods of time without tiring his hand or fingers whilst his initial effort to snap the gun from closed to open position against the sum of the spring pressure and the static head on the closure member need be no more than about 8 to 10 pounds.

The :closing operation reverses this series of events and the order in which the forces come into play wvith the desirable result that when the operator releases his squeeze upon the trigger the force of the spring 2d moving the closure member toward the seat of the valve is rapidly augmented by the effect of the fluid pressure in the chamber tending to slam the closure member onto the seat with accelerated motion to `achieve sharp, substantially instantaneous closing of the valve. The rapidity with which the gun may be changed from its full ofi to full on lcondition, and vice versa, tends mightily to diminish, if not utterly eliminate, the evils of spitting and otherwise which are caused by tardy or sluggish valve movements in varyyimg degrees depending also on the kind of paint and the collateral circumstance attending the spraying thereof.

There are cumulative advantages that flow from the small diameter of the wire W: It facilitates very high unit sealing pressures to be exerted upon it at the seal 48 with small frictional drag, and the smallness of its diameter reduces the blow-out pressure exerted upon it to a very small `fraction of the pressure in the chamber of the gun. This is illustrated by continuing our example `from the beginning of the cycle of operation with the gun in the on position with the spring compressed and exerting about 14 pounds tending to close the valve V. To effect motion of the closure member the spring will have to overcome friction between the wire W and the seal 41S, Whatever this value may be, plus the blow-out pressure lwhich the fluid in the chamber exerts upon the wire. If the frictional drag should be as much as 1 pound .and `blow-out pressure 1/2 pound, then the spring must exert force enough to overcome this 11/2 pounds in addition to providing the desired accelerating of the closure member. When, however, it comes to opening the valve (as described labove in relation to the snapaction which We achieve) blow-out pressure on the wire W aids the opening motion, of course, but frictional drag opposes the opening motion just as much as it opposed the closing motion. Since `the spring has had to be adjusted stout enough to overcome friction with a desirable margin to close the valve, then upon opening the valve, not only must frictional drag be overcome again but the strength which was added to the spring must be overcome as well. Therefore, if frictional drag should amount to as much as 1 pound, the net edect in the work of valve operation would be to :add Z pounds to the :force required to open (and hold open) the valve. Therefore, when we, in our invention, reduce this frictional force we eliminate much, if not all, of the 2 pounds extra force that would otherwise have to be overcome to open the valve. It also follows, that this reduction in friction pays an extra dividend: The less force required from the spring 20 to open the valve, the less force will be required to hoid it open.

We now revert to the valve, restrictor and nozzle at the forward, leiftward as viewed in FIG. 1, end of the gun and `continue our example of desirable sizes and proportions of the parts: The diameter of the seat 21 of the valve V was given at 0.112. With such a seat, we have found it advantageous to make the cylindrical orifice 38 in the hardened seat member 317 of the valve about 0.055 in diameter and about gyg flong with added rearwardly and outwardly flaring walls reaching to the -line of con- Si tact with the head 40 of the closure member at the circle of the seat 21. With the parts so proportioned, we provide a very much smaller orifice 39 in the restiictor plate 314 and prefer to form that orifice with a sharp edge facing the valve and an outwardly and forwardly flaring 'opening to the nozzle N whereby to cause a high velocity, turbulent and/tor turbulence-inducing io'w from the valve into the nozzle-a thing which per se has been known before and employed by -us yand others in the prior art. The bottom retaining vvall 65 of the restrictor assembly 33` has a central opening much larger than the restrictor orifice 39 and is not intended to modify the action of the restrictor. Our nozzle, however, takes novel advantage of the high velocity flow through the restrictor orifice 39 by virtue of the large cylindrical ante-chamber 66 formed coaxially with the axis of the valve and the axis of the orifice 39` and having a rounded, forward end of substantial dome shape, from the center and axis of which leads a secondary, dome-shaped ultimate orifice 67 through which paint is finally projected to atmosphere. Continuing our example of dimensions and proportions, the chamber 65 may be about 1A in diameter and of :about the same length. Preferably the volume of the chamber |66 is small as taught in our prior patent so :that the beneficent influence of the restrictor orifice, like the needle valve `orifice in our prior patent, will not be lost by remoteness from the discharge slot 63, and also, so that ebullient bubbles in hot paint will not burble out through the nozzle between shots7 of 4the gun to be whisked onto the work as an undesirable glob or droplet with the next foilowing shot. The orifice 67 may have its diameter from 0.010 to 0.035 `for efficient operation. The orifice 67 preferably has a sharp, circular inner edge intersecting the dome of the chamber 66. The orice 67 terminates leftwardly, as viewed in FG. 1, :in a slotted, vertical as viewed in FIG. 1, notch 6% according to known and our -own prior practice. We have thus provided a relatively slow, free liow of paint through the valve :and outlet 38, then sharp turbulence at, adjacent and through the orifice 39, at high speed in the orifice, then agitated flow in the ante-chamber 66 and finally the turbulent entrance of the pm'nt into and rapid Eliow through the final passage 0r orifice 67 and then the final ejection from the slot d3 lat high velocity and in the desired ilat fan shaped, feathered tail-free pattern.

The interior of the barrel B with the rearwardly opening interior of the valve V comprises the chamber C of the g-un with which the paint conducting hoses H communi- -cate via the swivel connectors 111-14, FGS. 1, 2, 2a and 5 8, through the openings 311, of which only the far opening for the far connector 12 appears in FIG. 1. The chamber C is intended 4to be supplied with paint through one of the hoses, and circulation, especially of hot paint, to maintain the desired temperature thereof in the chamber, is effected by known means, not shown, in a liuid circuit including a return via the other hose. Both the hoses H must resist bursting and leakage at high fluid pressures and temperatures, wherefor the hoses tend, naturally, to be stout and stiff, presenting a problem of effort and awkwardness to the user of the gun.

Where the hoses H depend from the gun as in FIGS. 1, 2 and 6 the swivel connectors 111 and 1-2 depend from the barrel but are given a rearward inclination to approximate parallelism with the grip R. That is to say, 'we prefer that the axes of the connectors 11 and 12 be parallel with each other and lie in a plane which is approximately parallel with the rearwardly inclined grip and intersects a reference plane that is normal to the axis a of the gun, i.e. the barrel, valve and wire W, in a line passing through the laxis and at an angle of about 10 to the reference plane. Each of the hoses is free to swivel about the respective axes of the connectors 111 and 12, and the rearward inclination of the hoses tends to locate or dispose the mid-lengths of the hoses that reach from the lioor to the gun vertically below the operators elbow while the operator is standing and aiming the gun approximately horizontally. Similarly, the upper-lengths of the hoses tend to lie vertically below the wrist of the operators hand that holds the gun. These relationships enhance the freedom and convenience with which the gun can be aimed and fired, and particularly swung in greater or lesser horizontal arcs about the vertical axes of movement at the operators elbow and wrist, or both. With substantial lengths of the hoses rising from the floor to the gun and traversing said vertical axes at acute angle-s, the operators swinging of the gun induces only gentle twisting of the hoses which .is largely accommodated by free swiveling of the hoses at the connectors 11 and 12. Prior practice which tended to dispose substantially the whole length of the hose-s between the iloor and the gun quite remotely from `any vertical lines passing through the operators elbow or wrist, required relatively great eiort to bend and twist the hoses beyond the possible accommodation of swivel connectors.

The barrel B of our gun is lremovably attached to the stock S, cf. FIGS. 2 and 2a, with symmetry about the axis a of the gun and barrel so that it may be secured to the stock selectively in either of two positions; (d) with the connectors downwardly, FIGS. 1, 2, 5 and 6 or, (2) with the connectors upwardly, FIGS. 7 land 8. The forward face 70 of the barrel-connect-ing-portion 71 of the stock, FIG. 2a, is smooth and flat. The portion 71 is integral with the body of the stock and joined thereto in its upper portion, and comprises also an integral depending part 72 as well as lateral extensions 73 which latter are pierced with bolt holes 74 through which attaching bolts or )cap screws 75, FIG. 2, detachably secure the barrel to the stock. The attaching portion 7'1 of the stock has a central bore 76, FIGS. l and 2a, coaxial with the axis a and the bore 61, which is receptive of the rearwardly extending, hollow boss 77 of the barrel, FIGS. l and 5, fand which is coaxial with the `axis of the barrel and aligns `the barrel coaxially of the gun. The I.D. of the bore '76 is greater than the O.D. of the boss 77 to accommodate a cylindrical insulating sleeve 78 and effect a snug iit of the boss relative to the bore and provide heat insulation of one from the other; the barrel tending to have the temperature of the hot paint in the chamber whereas the stock is sought to be kept comfortably cool or not uncomfortably warm to the ltouch of the operator. An insulating gasket 79, FIG. 1, interposed between the front face 70 of the stock and the rear face `80, FIGS. l and 5, of the barrel resists transmission of heat from the barrel of the stock axially. The barrel has tapped holes 8=1 aligned with the holes 74 of the stock receptive of the bolts or cap screws 75 for securing the barrel to the stock in axial alignment therewith and thermally insulated therefrom. Sinoe the bolt holes 74 and 81 have their axes in the horizontal plane of the axis of the gun, the barrel may be secured to the stock with equal facility `and equal symmetry to the operating parts of the gun, with the connectors either upwardly or downwardly as may be desired.

Frequently, to facilitate spraying operations, the paint hoses are suspended `from the ceiling, for from piping systems related to the ceiling in a vertical direction related to the gun to take much of the weight of the hoses and the gun away from the operator as suggested in FIG. 7. This is accommodated by our gun by the reversal of the barrel as described above. The operation of the gun and all its constituents will be the same and will retain all its advantages yfor each of the upside-down and rightside-up positions of the barrel. In FIG. 8 the gun and the barrel are related as in FIG. 7, but angled connectors 13` and 14 permit the hoses to lie horizontally adjacent the gun, and, as shown in FIG. 8, extend rearwardly, possibly over the shoulder of the operator who may use the gun for all the convenience that may be had thereby in the circumstance in which such disposition and arrangement may be useful.

While we have illustrated and described a preferred form `and embodiment of our invention, and have given speoiiic examples of sizes and proportions of parts that we have now found to be useful in the best present embodiment that we have presently perfected, still, changes, modifications and improvements will occur to those skilled in the art who come to use and enjoy our invention and understand our teaching thereabout, all without departing from the spirit and lsubstance thereof and hereof. Therefore, we do not care to be limited in the scope and effect of our patent for our invention to the forms, examples and embodiments thereof herein speciiically illustrated and described, nor in any other way or fashion inconsistent with the progress in the art which our invention has promoted.

We claim:

1. A paint gun having a chamber for paint under pressure, a discharge valve in the front of sa-id chamber, a spring in said chamber tending to close said valve, a tine, smooth, tension wire extending from within said chamber to without the rear of said chamber and connected to said valve for opening said valve against said spring from without said chamber, means closing the rear of said chamber and having a small, rearwardly extending opening for said wire with close clearance for said wire, a fluid seal adjacent said opening without said chamber slideably coacting with said wire and having a low .coeflicient of friction with said wire and having the quality of viscous iiurid, and means for continuously maintaining substantially constant fluid pressure in said seal in excess of the pressure of paint in said chamber and continuously tending to extrude said seal into said chamber through the clearance between said wire and said opening.

2. The combination of claim 1 wherein said seal comprises a body of polytetraiiuoroethylene, and said means for maintaining pressure in said seal comprises a sliding gland and a spring in stressed engagement therewith.

3. The combination of claim 1 wherein said seal comprises a body of polytetraiiuoroethylene, and said means for maintaining pressure in said seal comprises a sliding gland having a diameter of no more than about 5 to 10 times the diameter of said wire along with a spring in stressed engagement therewith.

4. The combination of claim l wherein said seal comprises a body of viscous material impervious to heat and chemical attack between about 0 F. and 500 F. and flowable in said clearance within said range of temperatures at pressures between about 1000 pounds per square inch to 5000 pounds per square inch.

5. The gun of claim 1 having a barrel containing said chamber and said bar-rel having a rearwardly disposed bore, wherein said means for closing said chamber cornprises a cylindrical member containing said opening and containing said seal and said last named means, said member having a sliding iit in and being removable from the forward end of said bore, fluid sealing means between said member and said bore, and means for limiting rearward movement of said member in respect to said bore.

6. A paint gun having a chamber for paint under pressure, a discharge valve in said chamber, means in said chamber tending to close said valve, a fine, smooth wire extending from within to without said chamber and acting in tension and connected to said valve for opening said valve against said means, means closing said chamber and having an opening for said wire with a close sliding it therewith, iiuid sea-ling means adjacent said opening without said chamber and closing said opening and slideably coacting with said wire and comprising a plastic annulus having a low coefficient of friction with said wire and comprising means for continuously maintaining pressure in said sealing means in excess of the pressure required to prevent paint from flowing from said chamber through said opening.

7. The combination of claim 6 wherein said means for maintaining pressure in said sealing means comprises a stressed yielding resilient element.

8. The combination of claim 6 wherein said sealing means comprises a body of plastic material impervious to heat and chemical attack between about F. ,and 500 F. and owable in said opening around said wire within said range of temperatures at pressures between about 1000 pounds per square inch to 5000 pounds per square inch.

9. A paint gun having a chamber for paint under pressure, a discharge valve in the front of said chamber, a spring in said chamber tending to close said valve, a iine, smooth, tension wire extend-ing from within said chamber to without the rear of said chamber a-nd connected to said valve for opening said valve against said spring, means closing the rear of said chamber and having an opening `for said wire, a uid seal adjacent said opening Without said chamber slideably coacting with said wire to seal said paint in said chamber, stressed resilient means for continuously maintaining pressure in said seal in excess of the pressure of paint exerted thereon and continuously tending to force said seal into said chamber between said wire and said opening, said gun also having a barrel containing said chamber and having a rearwardly disposed bore wherein said means for closing said chamber cornprises a cylindrical member containing said opening, said seal, said resilient means and a nut threadably engaging said member and adjustably stressing said resilient means, said member having a removable sliding tit in said bore, and means restraining said member from being blown `out of said bore.

10. A paint gun having a chamber for paint under pressure, a discharge valve in the front of said chamber, a spring in said chamber tending to close `said valve, a fine, smooth, tension wire extending from within said chamber to without the rear of said chamber and connected to said valve for opening said valve against said spring, means closing the rear of said chamber and having an opening for said \wire, a uid seal adjacent said opening without said chamber slideably coacting with said wire to seal said paint in said chamber, stressed resilient means for continuously maintaining pressure in said seal in excess of the pressure of paint exerted thereon and continuous-ly tending to force said seal into said chamber between said wire and said opening, said gun also having a barrel containing said chamber and having a rearwardly d-isposed bore wherein said means for closing said chamber comprises a cylindrical member removably disposed in said bore and having a central partition pierced coaxially of said bore by said opening and containing a coaxial stuiiing box for said seal behind said opening, and said last named means comprises a gland engaging said seal and slideable in said box, a spring in stressed engagement with said gland and a nut threadably coacting with said cylindrical member and engaging said spring and adjustably maintaining stress in said spring and pressure in said seal.

References Cited in the file of this patent UNITED STATES PATENTS 1,551,508 Smith Aug. 25, 1925 1,835,865 Hansen Dec. 8, 1931 2,339,036 Tea Jan. ll, 1944 2,559,544 Paasche July 3, 1951 2,568,052 Catranis Sept. 18, 1951 3,000,576 Levey et al. Sept. 19, 1961 

6. A PAINT GUN HAVING A CHAMBER FOR PAINT UNDER PRESSURE, A DISCHARGE VALVE IN SAID CHAMBER, MEANS IN SAID CHAMBER TENDING TO CLOSE SAID VALVE, A FINE, SMOOTH WIRE EXTENDING FROM WITHIN TO WITHOUT SAID CHAMBER AND ACTING IN TENSION AND CONNECTED TO SAID VALVE FOR OPENING SAID VALVE AGAINST SAID MEANS, MEANS CLOSING SAID CHAMBER AND HAVING AN OPENING FOR SAID WIRE WITH A CLOSE SLIDING FIT THEREWITH, FLUID SEALING MEANS ADJACENT SAID OPENING WITHOUT SAID CHAMBER AND CLOSING SAID OPENING AND SLIDEABLY 